DESCRIPTION: (Adapted from the applicant's Application) A central question in developmental biology is how a multicellular organism can arise from a single cell. In an effort to understand the complexity of the restricted expression of specific subsets of genes to a particular cell or tissue type, the investigators have compared the transcriptomes (the set of expressed genes) and propose to initiate preliminary studies to determine the feasibility of comparing the proteomes (the set of proteins) of immature and mature chicken dorsal root ganglia (DRG). The objective is to determine the function of a differentially expressed molecule, neural epidermal growth-factor like (NEL), and to extend the analysis of molecular differences to the proteome level. Specific Aim 1 proposes to determine the function of NEL during sensory neurogenesis. Specific Aim 2 plans to determine the molecular differences in the proteomes between immature and mature DRG. A proteomic analysis will be initiated by running 2D gels on E4.5 and E8.5 DRG and, based on their resolution, the feasibility of this approach will be determined. If successful, the investigators can conduct protein identification through mass spectrometric analysis.